Anastomosis, the surgical formation of a passage between two normally distinct organs or spaces, is a critical part of many surgical procedures. This is particularly true for coronary artery bypass graft (CABG) procedures in which one or more graft vessels are joined to coronary arteries. The distal end of the graft vessel is typically joined to the coronary artery distal to the stenosed or blocked portion of that artery, in order to improve the blood supply to the myocardium. The graft vessels normally used include the saphenous vein of the leg and the radial artery of the arm. After the graft vessels are harvested, they are cut to the correct length, and then joined on their proximal ends to a blood supply vessel, usually to the aorta. Thereafter, the graft's distal end is attached to the coronary artery. In an alternative procedure, the internal mammary artery (IMA) is used as a graft vessel. In this procedure the artery is temporarily clamped, severed at a location allowing enough length to be redirected towards the heart, dissected from the chest wall and arterial side branches, and then the distal end (pedicle) is attached to the lower anterior descending coronary artery (LAD) to improve or restore blood flow to the myocardium of the heart. In this case, the anastomosis (the suture attachment) is made only at the distal end, or pedicle, of the IMA.
For the grafting procedures mentioned above, the type of vascular anastomosis used is typically referred to as an end-to-side type. That is, the open end of the graft vessel is attached to the side of the target vessel. However, other types of anastomosis are used as well. The end-to-end type of anastomosis is common for joining together larger hollow organs such as bowel, but can also be used for heart bypass procedures, especially for cases where the arterial flow is completely occluded by the stenosis in the diseased artery.
Some surgeons choose to complete all the proximal anastomoses to the aorta before commencing the distal anastomoses to the coronary arteries. In contrast, others choose to complete the distal anastomoses first. Regardless of the order, when undertaking the distal anastomoses to the coronary artery, it is important that the vessel graft be held steady and adjacent the coronary artery, with a minimum of vascular trauma and a minimum of visual and surgical obstruction by instruments in the narrow operative field.
Currently vascular anastomosis is accomplished by hand suturing with a tiny, curved needle and very fine suture filament. The suturing method, however, is very time consuming and requires several minutes per anastomosis, even for an experienced surgeon. In some cases the blood flow in the newly joined vessels may be poor, and the surgeon must remove the stitches and repeat the suturing procedure. In surgical procedures involving multiple bypass grafts, the time accumulated for doing the suturing is very substantial, putting the patient at risk and increasing the cost of the surgical procedure.
Hand suturing also requires a high level of skill and is not easily mastered by many surgeons. The preferred type of suturing method for the anastomosis of blood vessels is where the needle is passed through the wall of the first vessel (such as the coronary artery) from the inside to the outside, and then passed from the outside to the inside of the second vessel (such as the graft vessel), so that when the suture is drawn tight, the inside walls of the vessel come together, intima-to-intima. This is to insure that the vessels heal together properly with a smooth layer of endothelial cells formed on the inside of the anastomosis. A single stitch would first be done in this manner at each of the heel and toe locations of the anastomosis, and then a running stitch would be made on each half of the anastomosis between the heel and toe along the periphery of the anastomosis.
It is especially difficult to suture if the anastomosis site is not easily accessed or viewed. For the standard CABG procedure, access to the heart is obtained via a median sternotomy in which the rib cage is split longitudinally on the midline of the chest, and the left and right rib cages are spread apart. Less traumatic means of access are becoming more widely used in recent years, including a cardiac procedure known as MIDCAB (Minimally Invasive Direct Coronary Artery Bypass). In one version of a MIDCAB, access to the heart is obtained by using a small, left thoracotomy (incision between the ribs on the left chest) directly above the heart. In this procedure, the surgeon's access to the heart and visibility of it are significantly reduced, and hand suturing is even more difficult than when using a median sternotomy. Other new developments in the surgical procedures have made conventional suturing even more difficult. More and more surgeons are operating on a beating heart to avoid the complications associated with using a heart lung bypass machine.
A number of devices for augmentation of the suturing techniques have been developed. These devices attempt with varying degrees of success to reduce the difficulty in repeatedly passing a needle and thread through the vascular walls. Recent examples are found in U.S. Pat. No. 5,571,090 issued to Sherts on Nov. 5, 1996, U.S. Pat. No. 4,803,984 issued to Narayanan on Feb. 14, 1989, and U.S. Pat. No. 5,545,148 issued to Wurster on Aug. 13, 1996. However, these devices have a number of disadvantages. In Sherts and Narayanan, the individual stitches must still be made one at a time, and therefore the procedure is still tedious and time consuming. The working ends of the Wurster and Sherts devices appear to obstruct the view of the needle tip and so precise placement of the stitch might be difficult in some situations.
Surgical staplers are widely used for the end-to-end or side-to-side anastomosis of large, hollow organs and are often easier to use than sutures. The two types of surgical staplers used in such procedures are the circular stapler and the linear cutting stapler. Both of these kinds of devices require that the stapling implements of the distal ends be inserted inside of the hollow organs to be joined together. However, such stapling devices which are small enough to be used inside blood vessels and which are still effective are not currently available to surgeons.
For any surgical device used for vascular anastomosis, it is extremely important that both the graft and the target vessel not be manipulated to the extent that significant trauma to the vessels occurs. Again, this is to insure that the vessels heal together properly and a smooth passage between them is created. Current methods of vascular anastomosis of a graft to the coronary artery require that blood flow be temporarily stopped using some kind of clamping device on each vessel proximal to the anastomosis site. These clamping devices can risk injury to the artery, thus comprising the long term viability of the vessel to maintain blood flow.
Because of the aforementioned considerations, there has been a need to provide a surgical device for facilitating a suture anastomosis of very small hollow organs, such as blood vessels. There has been a need to have such a device which is easy to operate and can perform the anastomosis quickly and efficiently. There has also been a need to have such a device which can allow blood flow to be maintained during the joining of the blood vessels. There has also been a need for such a device that requires minimal manipulation of the blood vessels. Such a device should allow rapid healing of the endothelial lining inside the blood vessels, and allow the vessels to be joined together intima-to-intima. Such a device should also be adaptable for use during traditional, open cardiac procedures (CABG) as well as in minimally invasive procedures such as MIDCAB procedures. The present invention provides such a device.